AVO 8 MkIII Restoration

​This AVO was previously owned by the FCO (Foreign Office) with a reference number of 00768.
FCO was a ministerial department from October 1968 to September 2020. The AVO 8 MKIII is probably dated around the 1968 time though there are no dates anywhere on the internals.
I found a price list published by AVO in 1968 which had the 8MKIII at £23&10shillings, which accounting for inflation would be £340 at today’s prices.

Initial state.

​Very dirty and the front glass has been pushed in, onto the meter movement. This is a common issue as the glass is only held in by a glue seal and 4 brass lugs, when picking up the AVO it was too easy to grab it front to back with the fingers or thumb pressing in on the glass, particularly if the strap was 'not trusted'!

​The battery compartment still had old batteries in which had long since exploded with corrosion everywhere.

It was good to find that these 15v batteries were still available, albeit that they cost more than I paid for the AVO!

​First job was to clean the case back and battery box, I tested various solvents on the Bakelite, including Water, Peroxide, Isopropanol, Acetone, Windex, WD40, MEK, none of which worked well, the most successful was UBIK2000, used to remove oxidation from conservatory plastics. The battery box was treated with White vinegar and fibre glass brushing.

​​The general condition of the internals was good and just needed the meter movement and the glass removing and refixing.

​​The movement itself tested OK, which was a relief but still needed dismantling to clean the dial face. I had to backtrack a bit on the solvents as I didn’t want to risk damaging the printing, the best solution was Windex (Windolene) as this removed the main muck but not the printing, I did test UBEK2000 on a small area... it restored the white area to pure white, but it also started to lift the print.

​​The front casing was thoroughly cleaned, as some of the lettering had already come off,
​I decided to completely remove it all.

​I then hand painted all the lettering back in.

​Fully reassembled after treating the leather strap with conditioner and adding new rubber feet to the back.

I tested the meter on various ranges against a Fluke multimeter and were in general within spec, I don’t have the equipment to test much of the A.C. range or voltages above 100v but as the lower ranges were OK it would seem reasonable to assume the higher ones were too. I noticed that someone had been in previously and ‘adjusted’ some of the DC Voltage dropper resistors, perhaps it had been in somewhere for a better calibration. As this was always meant to be a 'minimal intervention' restoration I decided not to make any adjustments myself. A calibration lab would be better suited for this. In previous employment we would have normally marked the meter as 'indicator only' when any form of compliance standard was required, and the meter had not been ‘calibrated’.

​As most of the results are well within spec. it reaffirms to me that this has at some time been in for calibration/testing.